Human Immunodeficiency Virus (HIV) affects millions of people worldwide, and the prevention of HIV through an efficacious vaccine remains a very high priority, even in an era of widespread antiretroviral treatment. HIV-1 is the most common and pathogenic strain of the virus, with more than 90% of HIV/AIDS cases deriving from infection with HIV-1 group M. The M group is subdivided further into clades or subtypes. An efficacious vaccine ideally would be capable of eliciting both potent cellular responses and broadly neutralizing antibodies capable of neutralizing HIV-1 strains from different clades.
The high genetic variability of HIV-1 makes the development of a HIV-1 vaccine an unprecedented challenge. In order to improve coverage of potential T-cell epitopes, and improve cellular responses, “mosaic” HIV-1 Gag, Pol and Env antigens, derived from HIV Group Antigen (Gag), Polymerase (Pol), and Envelope (Env) proteins, were described by others and developed in an attempt to provide maximal coverage of potential T-cell epitopes (e.g., Barouch et al, Nat Med 2010, 16: 319-323). The mosaic antigens are similar in length and domain structure to wild-type, naturally occurring HIV-1 antigens.
Sequences encoding mosaic antigens have been cloned in vectors, for example, such as recombinant adenovirus serotype 26 (rAd26), and these recombinant vectors have been used in vaccines to generate immune responses against HIV (see e.g. Barouch et al, supra; and WO 2010/059732). Viral vectors expressing such mosaic HIV antigens have proven to be effective in eliciting an immune response against HIV infection.
Another therapeutic strategy that has been explored for inducing immune responses against HIV is the use of trimeric HIV envelope proteins as immunogens in vaccines, such as gp140. The native envelope spike on the surface of HIV is trimeric. Examples of trimeric envelope proteins include clade C gp140 protein, and a mosaic envelope trimer protein, such as those disclosed in WO 2014/042942 and WO 2014/107744.
Clade C gp140 protein has previously been described e.g. in WO 2010/042942 and in Nkolola et al. 2010, but there was no focus on any pharmaceutical formulation work in those disclosures. The protein was in phosphate-buffered saline (PBS) in some of the experiments in those disclosures. Mosaic gp140 has been described previously e.g. in WO 2014/107744 and in Nkolola et al 2014, but again there was no focus on any pharmaceutical formulation work in those disclosures. The protein was in 25 mM Tris pH 7.5 and 150 mM NaCl in some of the experiments in those disclosures.
Trimeric HIV envelope proteins, such as gp140, are capable of inducing potent immune responses. Such envelope proteins can also be administered in combination with other HIV antigens, such as mosaic antigens, to provide enhanced immunity against HIV. However, the stability of the HIV envelope proteins as trimers is not optimal under conditions typically used for clinical and commercial manufacturing. The trimeric HIV envelope proteins are susceptible to both chemical and physical degradation. Moreover, many different factors, such as the buffer formulation, can affect the stability of proteins, and the effects are often unpredictable. For example, the use of HEPES buffer in protein formulations has been shown to result in generation of hydrogen peroxide when exposed to ambient light during the manufacturing process, which can impact the stability of the protein as well as other components in the formulation, such as surfactants. See, e.g., Baicu et al. Cryobiology (2002) 45(1) 33-48; Lepe-Zuniga et al. J. Immunol. Methods (1987) 103(1), 145; and Zigler et al. In Vitro Cell. Dev. Biol. (1985) 21(5), 282-287. It is desirable to have an HIV vaccine gp140 formulation that would be suitable for stability of different variants of gp140 protein, such as Clade C or mosaic gp140, and preferably with Aluminum Phosphate adjuvant as a single vial drug product (rather than being entirely dependent upon pharmacy mixing immediately prior to delivery of the vaccine), and in addition would enable drug product manufacturing meeting large late phase and commercial scale demands. It is generally unpredictable which combination of ingredients will result in a formulation that meets all these requirements.
Accordingly, there is a need in the art for improved formulations of HIV gp140 proteins with better stability under conditions used for clinical and commercial manufacturing in order to realize the full therapeutic potential of such trimeric envelope proteins. These formulations should also be compatible for use with additional HIV antigen(s), including vectors expressing HIV antigen(s), and/or adjuvants.